Editing Backflow prevention device (section)

==Regulatory requirements==
To prevent contamination due to back pressure, many health regulatory regimes require an air gap or mechanical backflow prevention assembly between the delivery point of mains water and local storage or use.<ref>{{Cite web|url=http://www.opsi.gov.uk/si/si1999/99114802.htm|title=The Water Supply (Water Fittings) Regulations 1999|accessdate=July 26, 2010| archiveurl= https://web.archive.org/web/20100823022423/http://www.opsi.gov.uk/si/si1999/99114802.htm| archivedate= 23 August 2010 | url-status= live}}</ref> Where submerged mains inflow is permitted,{{elucidate|date=March 2013}} a backflow prevention assembly is required, which protects the potable water system from contamination hazards. A [[check valve]] is a basic form of backflow prevention, but often more complex devices are required because check valves are not considered to be reliable, when compared to more sophisticated devices with redundancies and reduced-pressure zones.{{elucidate|date=September 2015}}

In many countries. approved backflow prevention assemblies are required by law, and must be installed in accordance with plumbing or [[building code]]s.{{examples|date=February 2012}}  A typical backflow assembly has test cocks and shut-off valves, and must be tested when installed, if relocated or repaired, and also on a periodic basis.{{citation needed|date=March 2013}}

In the US, the [[United States Environmental Protection Agency|Environmental Protection Agency]] (EPA) holds local water suppliers responsible for maintaining a certain amount of purity in potable water systems. Many states and/or local municipalities require annual testing of backflow prevention assemblies. In most cases, the law requires a double check (DC), reduced pressure principle device ([[Reduced pressure zone device|RP]]) device, or an air gap when backflow prevention is mandated.{{citation needed|date=March 2013}}